Abstract In this study, the effect of aggregate size and ambient temperature on the impact resistance of concrete was investigated experimentally. Also, it was tried to determine the behavior of normal and crushed stones in impact resistance, freeze–thaw, and compressive strength when used separately and together in concrete. No additives were used in the concrete samples. The consistency stability of fresh concrete is 80 mm. The Dmax of the aggregates is 16 mm and 31.5 mm. These specimens underwent successive impact tests at temperatures of 30 °C, 0 °C, and − 25 °C and were subjected to drops from heights of 25 cm and 30 cm. The resistance of the concretes to pressure and impact increased with a larger aggregate size. Notably, concrete samples containing crushed stone exhibited higher resistance to impact compared to those with normal aggregates. On moderate, the concrete samples at temperatures of 30 °C, 0 °C, and − 25 °C could withstand 12–14, 10–12, and 6–11 consecutive impacts, respectively. A discernible decrease in the resistance of concrete against pressure and impact was observed as the atmospheric temperature decreased.
Systems of building construction. Including fireproof construction, concrete construction
This work discusses an approach to solving geometric construction problems in which the given figure is included in a set ordered by construction steps. The flow of information is carried through the chain, allowing the original problem to be transformed and solved in a broader context. For demonstration, three classical tasks of construction are considered: proportional segments, a Gothic detail, and proportional angles.
The building blocks for irreducible smooth representations of p-adic groups are the supercuspidal representations. In these notes that are an expansion of a lecture series given during the IHES summer school 2022 we will explore an explicit exhaustive construction of these supercuspidal representations and their character formulas and observe a striking parallel between a large class of these representations and discrete series representations of real algebraic Lie groups. A key ingredient for the construction of supercuspidal representations is the Bruhat-Tits theory and Moy-Prasad filtration, which we will recall in this survey.
Sarra Mezaouri, Zine El-Abidine Kameche, Hocine Siad
et al.
Abstract This work investigates the combined use of waste glass aggregates (GA) and glass powder (GP) in cementitious mortars. For this reason, the optimized incorporation of GA by natural aggregates (NA) replacements was first studied after applying a surface roughening method with hydrofluoric acid. The compressive strength results were utilized to select the best mixture with GA. Then, different GP contents were added by cements substitutions to the optimized GA-based mortar. A control mortar without GA and GP amounts was also casted as a reference for comparison. The detailed mechanical, physical and durability properties of the resulted mixtures with combined GA and GP were assessed by considering the compressive and flexural strengths, ultra-sonic pulse velocity, alkali-silica reaction (ASR), rapid chloride permeability test (RCPT), magnesium sulphate attack and sulfuric acid resistance. The microstructure of different optimized (GA + GP)-combinations was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS)in order to analyse the interfacial transition zone (ITZ) between glass materials and the surrounding matrix. The results showed that the optimized composition with 75% GA and 25% GP was shown with high compacity and durability characteristics due to the increased GA/matrix ITZ and the formation of C–(N,K)–S–H products with C–S–H.
Systems of building construction. Including fireproof construction, concrete construction
Mohamed H. Makhlouf, M. Alaa, Gamal I. Khaleel
et al.
Abstract In this paper, the shear behavior of ferro-cement hollow beams is investigated experimentally and analytically. Ten reinforced concrete beams with cross-sectional dimensions of 100 × 200 × 1300 mm and a clear span of 1000 mm were cast and tested until failure under a two-point loading system. Ferrocement beams in this research contained either an autoclaved aerated lightweight brick core (AAC) or an extruded foam core (EFC) and were reinforced with either expanded metal mesh (EMM) or welded wire mesh (WWM). The structural behavior of the studied beams, including first crack, deflection, ultimate load, crack pattern, failure mode, and ductility index, was investigated. The experimental data were used to validate finite element models created with the ABAQUS finite element program. It can be concluded that the optimum performance of ferrocement beams can be achieved using beams with a second layer of expanded steel mesh as additional reinforcement, which led to an increase in the ultimate load and maximum deflection by 12.9% and 22.8%, respectively. Furthermore, the Numerical results agreed with the experimental results, where the ratio between the NLFE ultimate loads and the experimental ultimate loads varies between 1.02 and 1.07, with an average ratio of 1.04.
Systems of building construction. Including fireproof construction, concrete construction
Abstract Ultra-high performance concrete (UHPC) with excellent mechanical properties and durability is a promising material for reinforcement of existing normal concrete (NC) structures. In this paper, the shear failure behavior of the NC–UHPC interface was studied by the slant shear test and the SEM (scanning electron microscope) visualization test, considering influence of the substrate strength and the interface roughed treatment. As the NC substrate and the UHPC overlay are tightly combined at the interface transition zone (ITZ), the interface exhibits good slant shear performance, and the measured interfacial shear strength could reach 19.4 MPa with C40 substrate and 21.8 MPa with C50 substrate. In addition, the microstructure and composition of the ITZ, the possible interfacial failure modes, and the load-carrying mechanism of the interface under compression–shear force are revealed. The high interface roughness and the substrate strength have positive influence on the shear strength, and greatly affect the prone failure mode and the load-slip characteristic.
Systems of building construction. Including fireproof construction, concrete construction
Abstract In the context of a sustainable use of resources with the aim of the reduction of the CO2 footprint, the development of alternative concrete materials has attracted a great deal of attention. In this context, geopolymers, obtained from common clay deposits, are found to be interesting construction materials with very versatile properties. In this paper, a completely novel approach for the evaluation of the suitability of clays for the geopolymer formation is investigated. The method is based on simple and easy-to-handle IR spectroscopic measurements, through which the surface area under the OH stretching band in the IR spectrum of the clay can directly be correlated to the amount of reactive clay components. These reactive components are required for the success of the alkali activation of the clays in order to access geopolymers. Based on the theoretical reaction pathway of the geopolymer formation, the linear relationship between the OH stretching band area and the reactive components can be used for the estimation of the required activator amount for the alkali activation of calcined clays and predict the quality of the casted geopolymer mortar in terms of strength. This new method not only gives an insight into the suitability of a common clay for the geopolymer formation, but also facilitates a straightforward alkali activation procedure without tedious preliminary testing of the required activator amount.
Systems of building construction. Including fireproof construction, concrete construction
The use of data collection to support decision making through the reduction of uncertainty is ubiquitous in the management, operation, and design of building energy systems. However, no existing studies in the building energy systems literature have quantified the economic benefits of data collection strategies to determine whether they are worth their cost. This work demonstrates that Value of Information analysis (VoI), a Bayesian Decision Analysis framework, provides a suitable methodology for quantifying the benefits of data collection. Three example decision problems in building energy systems are studied: air-source heat pump maintenance scheduling, ventilation scheduling for indoor air quality, and ground-source heat pump system design. Smart meters, occupancy monitoring systems, and ground thermal tests are shown to be economically beneficial for supporting these decisions respectively. It is proposed that further study of VoI in building energy systems would allow expenditure on data collection to be economised and prioritised, avoiding wastage.
Ana Climent, Roberto Emparan, Javier M. Magan
et al.
We refine and extend a recent construction of sets of black hole microstates with semiclassical interiors that span a Hilbert space of dimension $e^S$, where $S$ is the black hole entropy. We elaborate on the definition and properties of microstates in statistical and black hole mechanics. The gravitational description of microstates employs matter shells in the interior of the black hole, and we argue that in the limit where the shells are very heavy, the construction acquires universal validity. To this end, we show it for very wide classes of black holes: we first extend the construction to rotating and charged black holes, including extremal and near-extremal solutions, with or without supersymmetry, and we sketch how the construction of microstates can be embedded in String Theory. We then describe how the approach can include general quantum corrections, near or far from extremality. For supersymmetric black holes, the microstates we construct differ from other recent constructions in that the interior excitations are not confined within the near-extremal throat.
Numerous industrial processes can be defined using distributed parameter systems (DPSs). This study introduces a two-stage spatial construction approach for real-time modeling of DPSs in cases of limited sensors. Initially, a discrete space-completion approach is created to recuperate the spatiotemporal patterns of non-monitored locations under sparse sensing. The high-dimensional space construction method is employed to derive continuous spatial basis functions (SBFs). The identification and adjustment of the nonlinear temporal model are carried out via the long short-term memory (LSTM) neural network. Eventually, the amalgamation of the derived SBFs and temporal model results in a spatially continuous model. The use of a cubic B-spline surface is validated as an effective solution for optimizing space construction in the sense of least squares approximation. Experimental tests conducted on a pouch-type Li-ion battery demonstrate the efficacy of the proposed modeling technique under sparse sensing. This work highlights the promise of sparse sensors in real-time full-space modeling for large-scale battery energy storage systems.
Aleksey A. Lopuhov, Igor M. Lukatsky, Yurij N. Osipov
et al.
The article discusses issues related to pilot operation of unmanned aircraft systems. This set of measures is not defined and not regulated by official documents such as state standards, government resolutions, orders, etc. This is the reason for the relevance of the presented paper which reveals the features of the organization and implementation of activities of EMERCOM of Russia aimed at improving the design, as well as technical, operational and repair characteristics of equipment, and also aimed at correction of operational documentation and investigation of new equipment.
Systems of building construction. Including fireproof construction, concrete construction
Abstract As a critical component for steel beam and concrete slab to work together, the strength of the shear connector affects the flexural load capacity and stiffness of the composite beam. Connectors were generally studied for longitudinal shear resistance. However, transverse shear needs to be considered when the main beam is far away and the transverse connection is weak. In this paper, an angle connector pre-embedded in the precast slab was proposed, and its pre-embedded position makes it exhibit better transverse shear resistance. To assess the strength, stiffness, and slip capacity of the angle connector, two groups of composite beam with precast slabs negative moment flexural were tested, then several finite element groups were simulated in push-out test. The test variable was the existence of angle connectors, and the variables simulated were the yield strength of the angle connector and its flange thickness. The results showed that the composite beam with angle connectors has greater stiffness than ordinary ones, with little difference in flexural strength capacity and less slippage. The results show that angle connectors can replace extending rebars in precast slabs, which will reduce construction costs. In addition, a new design equation was proposed, including the yield strength of the connector and the thickness of its flange which are not unified in the current equations. The simulations determined the strength of the angle connectors in relation to the yield strength of the angle connector and its web thickness.
Systems of building construction. Including fireproof construction, concrete construction
Alexander Gladwin Alex, Tsegay Gebrehiwet Tewele, Zeyneb Kemal
et al.
Abstract Pioneering studies have been conducted on alternative cementitious material in the manufacturing of conventional concrete to reduce carbon emission and improve the overall efficacy. However, there are limited studies on eco-friendly materials with low calcium fly ash. This study aims to examine the strength fly ash geopolymer concrete and reduce carbon emission. In this investigation, flexural test is done for conventional and geopolymer concrete (GPC) beam samples after the fulfillment of rest period and 24 h steam curing at 60 °C. The experimental results prove that the initial characteristics of both specimens are almost similar. When GPC specimens reached the service, yield, and failure stages, the load carrying capacity, deflection increased up to 21.5 and 8.75%, respectively and better load bearing capacity, moment resistance, and crack propagation were observed more than in conventional cement. Fresh property test results indicated the achievement of standard workability without the addition of any admixture. Our study show that low calcium based geopolymer can be used as an efficient material for the alternate of cement in cement-based industries with eco-friendly nature.
Systems of building construction. Including fireproof construction, concrete construction
Xiangguo Wu, Xuesen Zhang, Hom Bahadur Bhattarai
et al.
Abstract Based on the conceptual design of an advanced wind turbine tower system, use of ultra-high-performance cementitious composites material with compressive strength of 200 MPa (UHPC-200) is proposed to ensure high durability and ductility of the UHPC hybrid wind turbine tower. Key design parameters are proposed for the structural design of a 3-MW wind turbine. The material properties, mixing compositions, simplified constitutive relationship, and model parameters are outlined. Using nonlinear finite element analysis, the effects of wall thickness, wall thickness ratio, and prestressing tendon on the structural performance including the longitudinal stress field, lateral displacement, stress concentration at the transition zone between the middle and bottom segments are evaluated. Based on the stress-field analysis, the design limitation of the segmental wall thickness and its ratio is recommended. The numerical results show that the tower with the wall thickness ratio of 2:3 (i.e., thickness 200–300 mm) with prestressing tendons is an optimal design for the UHPC hybrid tower. The results of this study can be used as a reference for the engineering design of a new type of UHPC hybrid wind turbine tower.
Systems of building construction. Including fireproof construction, concrete construction